Industrial networks play a big role in industrial automation, manufacturing, process control, and other industrial related businesses. Until recently, industrial processes and equipment would communicate with each other using one of several possible specialized open or proprietary protocols, such as Modbus, HART, Profibus, CANopen, DeviceNet, FOUNDATION Fieldbus, PROFINET IO, etc [1][2]. These are all specialized networking technologies tailored for industrial automation, manufacturing, process control.
Currently, it is not uncommon to see a manufacturing facility, for example, having multiple parallel networks as depicted schematically in FIG. 1: a control network 1 (for automation, manufacturing, process control), a voice network 2 (for traditional voice communication), and a data or Information Technology (IT) network 3 for normal IT networking (that is, for interconnecting computers, servers, printers, etc.). It is clear that there are significant disadvantages to this arrangement:                Each network requires its own network administration and management.        Each network requires its own set of maintenance and support staffs with the right skills.        Each network requires its own set of spares parts, inventory, etc.        Provisioning redundancy in the network results in a higher cost of network design and installation.        The overall footprint of the networks can be very large—taking up significant physical space. As space is normally at a premium (or at least costly) for most businesses this can be an additional cost or problem.        
However, many industrial networks are currently migrating from legacy industrial protocols to packet based technologies like Ethernet and IP. Ethernet has emerged as a viable alternative to the traditional industrial protocols simply because it is much cheaper, readily available, and proven to be effective for networking.
As such, there is growing interest in the industrial community to use available “data-centric” protocols such as Ethernet as the transport protocol for industrial networks (as shown schematically in FIG. 2 where a single integrated packet network 4 connects all functions of the business). Consolidating all industrial business processes on a common packet network offers the following benefits:                By using a computer network, various services such as control messaging, voice, video, and data can be multiplexed, switched, and transported together under a universal format.        Consolidation of separate control, voice and data (IT) networks offers significant savings in both capital and operational expenditure.        Full integration results in simpler and more efficient network administration and management.        Full integration will also reduce redundant hardware, communications facilities, and support staffs.        The higher bandwidth of fiber optics technologies, and the advent of high-speed network elements (e.g. routers and switches) are major drivers of the current trend towards network consolidation.        With a common network transport format, new services (e.g., video conferencing, collaborative computing, pervasive computing, etc.) can easily be introduced into the system.        
Ethernet is a major carrier for other networking protocols; Ethernet can pretty much carry any other protocol whether open or proprietary. The benefits of adopting packet technologies like Ethernet are as follows:                Increased speeds from 10 Mbit/s up 10 Gbit/s (and even more with 40 and 100 Gbit/s Ethernet now being developed) compared to 9.6 Kbit/s with RS-232.        Ability to work over copper (e.g., Category 5e, Category 6, etc) cables, optical fiber and wireless medium (e.g., IEEE 802.11 protocols).        Increased distance especially when using Ethernet over optical fiber.        Ability to use standard networking equipment and software (e.g., access points, routers, switches, hubs, etc.), cables and optical fiber, which are much cheaper and offer greater flexibility than the equivalent serial-port and industrial bus based devices.        Ability to deploy more than two nodes (multiple nodes) on a link, which was possible with RS-485 but not with RS-232.        Ability to deploy and configure peer-to-peer architectures rather than the master-slave ones common in traditional industrial networks.        Better interoperability and connectivity since all one needs is to equip the nodes on the network with Ethernet interfaces.        
The current trend shows that the industry has embraced Ethernet as the protocol of choice for industrial networking. However, there are certain difficulties in using Ethernet for industrial processes, most of which require real-time processing. Ethernet was initially developed as a data oriented protocol and was not designed with the inherent real-time and loss-less data transport capabilities found in many traditional industrial protocol.
These limitations of Ethernet often call for adding special functionalities in an Ethernet (or other packet) network to address the special needs of automation, manufacturing, process control processes.
One such situation is the remote control of an electric motor over a packet network as illustrated schematically in FIG. 3. Remote motor control plays a major role in automation, manufacturing, process control.
The area of control applications over IP (packet) networks has recently gained significant interest in the research community [6][7][8]. Due to the complex nature of control over IP packet-based networks, several researchers have devised different approaches to deal with the stochastic nature of the packet delay variations. In order to deal with the packet delay variations, many approaches attempt to replace practical controllers that exist in industrial applications such as the proportional-integral (PI) controller with other controllers [9][10][11]. This replacement is in general expensive and requires extensive amount of time to replace all the existing controllers.
In [12] a methodology to improve the widely used PI controller over IP networks was proposed. Specifically the optimal PI controller gains are scheduled in real time in accordance to the monitored IP network traffic allowing for a more dynamic approach to control system implementation.
In [13] a networked control system over Wireless LAN (WLAN) based on the separation principle of Linear Quadratic Gaussian (LQG) control with random delays and packet loss in the feedback loop improves the performance.
A method to control the speed of the DC motor through IP networks with packet loss has been also introduced in [14]. The method is tested through speed control experiments of a commercial DC motor. The effectiveness of reducing the negative influences of packet loss is demonstrated by adopting a PI controller with a Smith compensator.
In [15] an approach that modifies and enhances conventional systems is achieved through adopting a model-based networked predictive control scheme based on round-trip time delay measurements.
In [16] a technique to provide means to transfer time-critical information between devices over Ethernet-IP network was proposed for large industrial control or automation solution. The technique is at the protocol/application layer and does not address the critical issue of harnessing synchronization to control motors.
Another technique that deals with motor control over packet networks was proposed in [17] where an applet-based system is implemented to enable control mechanism between a client and a server. Although this approach addresses the application layer of control over packet, it lacks relevance and practical implementation of control algorithms at the physical layer.
Accordingly, the present invention seeks to provide a new technique for remote control of a motor (particularly a DC motor) over a network (such as a packet network). Some applications of speed control over packet networks in process control and energy conservation are to allow smoother operation of a process, acceleration control, allow different operating speed for each process recipe, compensate for changing process variables, allow slow operation for setup purposes, adjust the rate of production, allow accurate positioning, and control torque or tension of a system.